OTTAWA -- Justin Trudeau may be a boxing victor and a fundraising champion, but fellow Liberal leadership contender Marc Garneau says his resume isn't a knockout.

Garneau, who is largely seen as Trudeau's main challenger in the leadership race, said he isn't going to drop questions on the Quebec MP's credentials.

Garneau first raised the resume issue during the third Liberal leadership debate in Mississauga, Ont. this weekend, but vowed to push the frontrunner on it.

"I will definitely continue to challenge Justin on basically his resume. No question about it," Garneau said in an interview Tuesday. "I am in this to win"¦I'm the person with the most substance, the most demonstrated leadership experience."

Garneau has not questioned Trudeau for collecting at least $277,000 to deliver speeches to charities and school boards since being elected in 2008.

"Justin has to answer to anybody who may feel differently about his particular situations. I'm not going to comment on that," Garneau said.

NDP MPs, however, have taken aim at Trudeau over the paid events.

NDP House leader Nathan Cullen has suggested the move could constitute "double-dipping", as Trudeau is paid to be an MP and he may have missed time on the Hill to work the public speaking circuit.

"I guess Justin's been in the leadership campaign for years now," Cullen said.

Liberals will select a new boss in Ottawa on April 14.